I Kappa B

**Semantic type:** Amino Acid, Peptide, or Protein

**Definition:** A family of proteins that bind to the nuclear localization signal (NLS) domains of the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-kappaB) transcription factor complexes. This sequesters NF-kappaB in the cytoplasm and prevents its binding to the activation domains of target genes in the nucleus. Phosphorylation of I kappa B proteins, which is catalyzed by cytokine-activated I kappa B kinases (IKBK; IKK), disrupts binding to NF-kappaB and induces the degradation of I kappa B; this allows NF-kappaB to enter the nucleus and activate the transcription of target genes.

**Synonyms:** - I-Kappa-B - IKB - IKappaB - IkappaB - Inhibitor of Kappa B - NF-Kappa B Inhibitor - NF-Kappa-B Inhibitor - NFKB Inhibitor - NFKBI - Nuclear Factor Kappa-B Inhibitor - Nuclear Factor of Kappa Light Chain Gene Enhancer in B Cells Inhibitor